As a raw material for housing of mobile devices (such as notebook-type or tablet-type personal computers, mobile phones such as smartphones, digital cameras, digital video cameras), a thermoplastic resin composition (such as ABS resin, polycarbonate resin/ABS resin, polyamide resin), or a composition in which the thermoplastic resin composition has been reinforced by an inorganic filler are widely used.
As a method of manufacturing a housing, in general, a method of molding the thermoplastic resin composition by injection molding by which the shape of housing can be freely molded to some extent is applied.
Recently, with respect to the housing of mobile devices, a characteristic for making more thinner housing, a characteristic for satisfactorily enduring impact or load when the housing is present in a bag, and a characteristic for providing unpainted housing to reduce cost are demanded. In order to satisfy these demands, with respect to the thermoplastic resin composition used in a housing, high weld strength and heat resistance, and excellent moldability during molding are required as well as high rigidity and mechanical strength (impact resistance) of a molded article.
However, thermoplastic resin composition such as ABS resin, polycarbonate resin/ABS resin or polyamide resin, which has not been reinforced by an inorganic filler, show low rigidity, and therefore, the demand for a thinned housing cannot be realized. Since polyamide resins have high moisture absorbency, warpage and dimensional change and deterioration in appearance over time is likely to occur after molding.
Thus, as a thermoplastic resin composition used for a housing, a reinforced thermoplastic resin composition in which rigidity of ABS resin or polycarbonate resin/ABS resin is enhanced by adding an inorganic filler such as glass fibers or carbon fibers has been studied.
Although the reinforced thermoplastic resin composition containing ABS resin or polycarbonate resin/ABS resin as a main component has high rigidity and can realize a thinned housing, weld strength and impact strength of the molded article is insufficient. Although the reinforced thermoplastic resin composition containing polyamide resin as a main component exhibits excellent weld strength when a molded article is molded, the problem with respect to warpage cannot be solved. The problem is caused by moisture absorbency of the molded article after molding, and a solution based on the molded raw material has not been proposed.
As a reinforced thermoplastic resin capable of providing a molded article having high impact resistance, the following compositions have been proposed.
(1) A reinforced thermoplastic resin composition containing an aromatic polycarbonate resin, a graft copolymer, a glass fiber in which the surface thereof has been treated with a water-soluble polyurethane, a glycidyl ether unit-containing polymer and a phosphoric acid ester-type flame retardant (Patent Document 1)
(2) A reinforced thermoplastic resin composition containing an aromatic polycarbonate resin, a fiber-type filler in which the surface thereof has been treated with polyamide and a lubricant having a carboxyl group (Patent Document 2)
As a reinforced thermoplastic resin capable of providing a molded article having excellent mechanical strength, the following compositions have been proposed.
(3) A reinforced thermoplastic resin composition containing an aromatic polycarbonate resin, a thermoplastic polyester resin, a thermoplastic elastomer, and a glass fiber in which the surface thereof has been treated with a silane coupling agent and an epoxy resin (Patent Document 3)
(4) A reinforced thermoplastic resin composition containing a polycarbonate resin, a rubber containing polymer, and a carbon fiber converged in nylon-based convergence agent (Patent Document 3).